A. Technical Field
This invention relates generally to multiprotocol label switching in optical communication networking systems, and more particularly, to a generalized multiprotocol label switching fast re-route around a network event.
B. Background of the Invention
The Internet's network layer has three major components, the IP Protocol, the routing component, and the facility. The IP protocol determines addressing conventions, datagram formats, and packet handling conventions. The routing component determines the path a datagram follows from a source to a destination. Examples of these protocols are Routing Information Protocol (“RIP”), Open Shortest Path First (“OSPF”), and Border Gateway Protocol (“BGP”). The facility reports errors in datagrams and respond to requests for certain network-layer information and is known as the Internet Control Message Protocol (“ICMP”).
In a datagram network, each time an end system wants to send a packet, it stamps the packet with the address of the destination end system and then transmits the packet on the network. As a packet is transmitted from a source to a destination, it passes through a series of routers. Each of these routers use the packet's destination address to forward the packet onto the next appropriate network node. Specifically, each router has a forwarding table that maps destination addresses to link interfaces. When a packet arrives at the router, the router uses the packet's destination address to lookup the appropriate output link interface in the forwarding table. The router then forwards the packet to that output link interface.
A method used by routers to determine the appropriate path onto which data should be forwarded is a routing protocol. The routing protocol also specifies how routers report changes and share information with the other routers in the network that they can reach. A routing protocol allows the network to dynamically adjust to changing conditions, otherwise all routing decisions have to be predetermined and remain static.
An intra-autonomous system routing protocol is used to determine how routing is performed within an autonomous system (hereinafter, “AS”). Intra-AS routing protocols are also known as interior gateway protocols (hereinafter, “IGP”). Historically, two routing protocols have been used extensively for routing within an AS in the Internet: RIP and OSPF. A routing protocol closely related to OSPF is the Intermediate System to Intermediate System (hereinafter, “IS-IS”) protocol.
Internet addressing and forwarding are important components of the Internet Protocol (hereinafter, “IP”). There are two versions of IP in use today, the deployed IP protocol version 4, which is usually referred to simply as IPv4 and IP version 6, which is usually referred to as IPv6.
OSPF is a routing protocol that determines the best path for routing IP traffic over a TCP/IP network based on distance between nodes and several quality parameters. For example, in FIG. 1a client signal has a source node A 110 and a destination node D 130. OSPF determines the best path for the packet is from node A 110 to node E 120 to node D 130. This path is considered the chosen or active path for the packet. The path is based on routing protocols, in which each node performs a look up function, within a forwarding table, when the packet arrives at the node to determine the shortest hop to the next node or final destination of the packet. With OSPF, a router constructs a complete topological map of the entire autonomous system.
For example, in FIG. 2 the chosen path is node A 110 to node E 120 to node D 130. A break 200 may occur between node E 120 and node D 130 thus the packet must be re-routed to reach its intended destination node D 130. When this happens, RIP modifies the local routing table and then propagates this information by sending advertisements to its neighboring routers. As in FIG. 2, node C 170 may receive the datagram and provide an alternate route 210 to node D 130 based on the next shortest path.
The aforementioned routing protocols mainly support a unicast (i.e., point-to-point) communication, in which a single source node sends a packet to a single destination node. In broadcast routing, the network layer provides a service of delivering a packet sent from a source node to all other nodes in the network; multicast routing enables a single source node to send a copy of a packet to a subset of the other network nodes.
In prior internet architecture, a multicast packet is addressed using address indirection. That is, a single identifier is used for the group of receivers, and a copy of the packet that is addressed to the group using this single identifier is delivered to all of the multicast receivers associated with that group. In the internet, the single identifier that represents a group of receivers is a class D multicast address. IP multicast packets are identified by using a range of multicast addresses. The addresses within this range are reserved for specific purposes. For example, 224.0.0.1 means all nodes on the subnet, while 224.0.0.2 means all routers on the subnet.
Multiprotocol Label Switching (hereinafter, “MPLS”) is a standard from the IETF for including routing information in the packets of an IP network. MPLS is used to ensure that all packets in a particular flow take the same route over a backbone. MPLS router attaches labels (tags) containing forwarding information to outgoing IP packets. The routers within the core, known as label switch routers (hereinafter, “LSRs”), quickly examine the label and forward the packet per its directions without having to look up data in tables and compute the forwarding path each time.
Generalized Multiprotocol Label Switching (hereinafter, “GMPLS”), enhances MPLS architecture by the complete separation of the control and data planes of various networking layers. GMPLS enables a seamless interconnection and convergence of new and legacy networks by allowing end-to-end provisioning, control and traffic engineering (hereinafter, “TE”) even when the start and the end nodes belong to heterogeneous networks.
GMPLS is based on the IP routing and addressing models. The common control plane promises to simplify network operation and management by automating end-to-end provisioning of connections, managing network resources, and providing the level of QoS that is expected in the new applications.
In summary, GMPLS extends MPLS functionality by establishing and provisioning paths for: TDM paths (SONET), FDM paths (Light Waves), and Space division multiplexed paths (Photonic Cross-Connect). Thus, in a WDM optical networking system, it is the ability to route a data transmission based on the wavelength of light that carries it. The routing device only analyzes wavelengths (light frequencies) to make its forwarding decisions rather than inspecting fields within each packet. GMPLS adds numerous enhancements to MPLS in order to support optical networks.
As mentioned above GMPLS is critical to routing and forwarding in optical system networks. An extreme need for the fast routing and re-routing of packets around a network event, such as a failure, are essential as network speeds and complexities increase in today's optical networks.